Researchers from Tel Aviv University have identified a gene in wild wheat that regulates grain size and nutrient distribution; reducing its activity in laboratory experiments produced larger and heavier grains, containing more protein, iron, and zinc.
Wild wheat, from the ancestors of theWheat Modern, may provide breeders with a new genetic tool for improving grain size and nutritional composition. Researchers at Tel Aviv University have identified a gene in it that regulates seed development and the distribution of nutrients within it. When they reduced the gene's activity in several experimental systems, the result was larger and heavier grains, containing more protein, essential amino acids, and minerals including iron, zinc, and molybdenum.
The study, published in the journal Plant, Cell & Environment, does not yet present a commercial variety ready for sowing in the fields. It identifies a genetic mechanism and shows in several wheat varieties and several experimental methods that changing its activity affects grain size and composition. The findings may serve as a basis for breeding and improvement programs, but it will be necessary to test the plants in field trials and ensure that the improvement in the individual grain is also reflected in a stable agricultural yield.
The study was led by Dr. Zachariah Haber The late Dr. Devinder Sharma and Dr. Manas Frosty, postdoctoral fellows from Dr. Nir Sadeh at the School of Plant Sciences and Food Security and the Cereals Research Institute at Tel Aviv University. Researchers from the University of Haifa, the Agricultural Research Administration – Volcani Institute, and Ben-Gurion University of the Negev also participated in the study.
Dr. Haber was killed in action in the Gaza Strip in January 2024, while he was in the midst of his doctoral dissertation. His doctorate was awarded posthumously, and the research was completed in Dr. Sade's laboratory. Sharma, Haber, and Frosty are credited in the article as having contributed equally.
The gene library lost during domestication
Wild emmer wheat, Triticum dicoccoides, grew in the Fertile Crescent and is one of the ancestors of modern cultivated wheats. Over thousands of years of domestication and breeding, humans have repeatedly selected plants with agriculturally beneficial traits, including high yields, uniform ripening, and grains that are easy to harvest and process.
The process made it possible to turn wheat into one of the world's most important food crops, but it came at a genetic cost. Selection for a limited number of traits and varieties reduced much of the variation that existed in wild populations. Wild wheat has preserved many versions of genes that evolved under different conditions of heat, dryness, cold, and humidity, and therefore serves as a kind of natural library of evolutionary solutions.
To search for such solutions, the researchers analyzed about 460 lines of wild wheat collected from different climatic regions of Israel. They compared the genetic data with their grain weight, area, and nitrogen content. Analysis of the connections across the genome pointed to a central site on the long arm of chromosome 2B, known as 2BL.
In this region, a gene encoding a B3 family transcription factor was identified. Transcription factors are proteins that help regulate the activity of other genes. The researchers named the gene B3-SG, short for B3-Seed Growth, and found that it acts as a brake that limits seed growth and affects how carbon and nitrogen are distributed within it.
Same effect in several wheat varieties
Identifying a statistical association between a genetic variant and a trait does not by itself prove that the gene is the cause of the trait. Therefore, researchers tested the finding in several ways and across several genetic backgrounds.
The wild wheat-derived fragment was first introduced into the six-chromosome bread wheat varieties Chinese Spring and Bethlehem. The fragment also increased grain weight in a cultivated wheat background. Mutations that disrupted gene activity were then tested in the four-chromosome Kronos wheat variety, which also produced larger grains.
In another step, the team usedgenetic editing Type CRISPR/Cas9 in the bread wheat variety Fielder. Here too, inactivation of the gene or reduction of its activity increased grain weight and nitrogen content. Replication of the result in wild wheat, durum wheat, and bread wheat strengthened the conclusion that B3-SG is a negative regulator of seed growth at different ploidy levels.
Chemical tests showed that the change was not limited to size. In the grains where the gene activity was impaired, increases were found in essential amino acids, sugars, fats, nitrogen, and minerals including zinc, iron, and molybdenum. Analysis of gene activity indicated an amplification of pathways related to fatty acids, nitrogen, and phenylpropanoid compounds, along with a reduction in certain pathways of carbohydrate metabolism and sugar transport.
A hint for adapting to a changing climate
The researchers also found that two major natural variants of the genetic region are not randomly distributed. One variant is more common in hot, dry regions, while the other is more common in cooler, wetter regions. The distribution suggests that the gene has been involved in adapting wild wheat to different environmental conditions over time.
This does not mean that disabling the gene alone will make wheat more drought or heat tolerant. The link between genetic variants and climate suggests a promising research target, but agricultural adaptation is a complex trait influenced by many genes and the interactions between them and soil, water and temperature.
According to Dr. Sadeh, wild wheat is a genetic pool built over thousands of years of evolution under changing environmental conditions. Identifying genes that simultaneously affect grain size and nutritional quality may help develop varieties that will provide a higher quality harvest even under challenging growing conditions.
There is still a long way to go from the lab to the field.
The study provides genetic, molecular and biochemical evidence that the gene affects grain development, but practical questions remain. A larger grain does not necessarily guarantee a higher yield per dunam: the number of ears, the number of grains per ear, the duration of growth, water consumption, disease resistance and baking quality must also be examined.
It is also important to examine whether the increase in nutrient concentration is maintained in commercial varieties and under different field conditions, and whether the change in the gene has undesirable effects on other parts of the plant. Only after extensive cultivation and field trials will it be possible to determine whether the gene can actually contribute to a larger and more nutritious food supply.
However, the study demonstrates why the wild relatives of cultivated plants are important for food security. Traits that were not selected for during domestication, or that were lost during breeding, may become beneficial as agriculture is forced to cope with a changing climate and increasing demand for food. In this case, genetic material preserved in wild wheat in Israel may offer a new starting point for improving one of the most important crops in human nutrition.
Questions and Answers
What is emmer wheat?
This is a wild wheat species that grows in the Fertile Crescent and is considered one of the ancestors of cultivated wheats. It maintains a wider genetic diversity than that found in many agricultural varieties.
What did the researchers discover?
Researchers have identified a B3 family transcription factor that regulates seed growth and nutrient distribution. Reducing its activity in several wheat varieties produced larger, heavier grains and altered their nutritional composition.
Is the improved wheat already available to farmers?
No. This is basic and applied pre-commercial research. Field trials, variety breeding, and yield, stability, and quality testing are required before the discovery can be used in large-scale agriculture.
How is the discovery related to climate change?
Different natural variants of the genetic region have been found in wild wheat populations from hot, dry regions versus cool, humid regions. This suggests a role in environmental adaptation, but does not yet prove that gene inactivation per se confers heat or drought tolerance.
The scientific article
More on the subject on the science website
For the original publication: Tel Aviv University – The Superpowers of Ancient Wild Wheat
